High temperature bleaching of aliphatic sulfonates

ABSTRACT

ALIPHATIC SULFONATE DETERGENTS CAN BE EFFECTIVELY BLEACHED BY HYPOCHLORITE AT ELEVATED TEMPERATURES PROVIDED THAT THE REACTION IS QUENCHED.

Jan. 4, 1972 HIGH TEMPERATURE BLEACHING OF ALIPHATIC SULFONATES Filed July 1,

TEMPERATUREXC.

s. H. SHARMAN 3,632,515

2 Sheets-Sheet 1 HIGH TEMPERATURE HYPOCHLORITE BLEACHING OF ALI PHATIC SULFONATES TIME, MINUTES,

TO START OF COLOR REVERSION FIG.1

l N V E NTO R Jan. 4, 1972 s. H. SHARMAN 3,632,515

I HIGH TEMPERATURE BLEACHING OF ALIPHATIC SULFONATES Filed July 1, 1968 2 Sheets-Sheet 2 EFFECT OF TIME CN BLEACHING AT VARIOUS TEMPERATURES 3.07 NGOCR 370 \To 302 i AT 0 MIN. AT 60 MIN.

O! o a U 180- l,- w 115C. l K

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x 80C. 120- \g x x 0 1o 20 3o 40 so so TIME, MINUTES FIG.2

INVENTOR w. SHA MAN BY v W ATTdRN EYS United States Patent Int. Cl. C11d 7/54 U.S. Cl. 252-95 9 Claims ABSTRACT OF THE DISCLOSURE Aliphatic sulfonate detergents can be effectively bleached by hypochlorite at elevated temperatures provided that the reaction is quenched.

This invention relates to a method for the reduction of color in aliphatic sulfonates. More particularly, it relates to the reduction of color in aliphatic sulfonates obtained by the reaction of sulfur trioxide with olefinic nonaromatic hydrocarbons by the use of hypochlorite bleach at elevated temperatures.

It is known to produce sulfonates by the reaction of sulfur trioxide with alkenes (see for example, U.S. 2,061,619; 2,061,620; and 2,094,451) and that the vigor of sulfur trioxide in these reactions is also responsible for the production of much undesirable color. It is also known to treat these sulfonates with sodium hypochlorite bleach (see for example, British Patent 983,056) at temperatures in the range 20l00 C. and to thereby improve the color properties of the aliphatic sulfonates. Normally in the conventional production and processing of the aliphatic sulfonates, after the sulfur trioxide-olefin reaction, caustic is added to the crude product and a hydrolysis step is carried out preferably at elevated temperatures, for example in the range 100150 C. in view of favorable reaction-rate-temperature factors. Similarly, it would be desirable as a time saving expedient in the manufacturing process to concurrently bleach and hydrolyze the aliphatic sulfonate. However, in the latter case the experience is that the product obtained has surprisingly a very bad color although it is reasonable to expect that the bleaching reaction of the hypochlorite should also be accelerated by the higher temperature.

It has now been found that in the bleaching of sulfur trioxide-derived aliphatic sulfonates using hypochlorite at temperatures above about 90 C. and particularly in the range 100150 C. a rapid color reversion occurs after an initial decolorization. Thus for satisfactory reduction of color, reaction times during bleaching should be in the range from about 1-30 minutes with the shorter reaction times corresponding to the higher bleaching temperatures. Thus, in general for satisfactory concurrent hydrolysis and decolorization of a sulfur trioxide-derived aliphatic sulfonate, the bleach must be introduced into the reaction system after the hydrolysis has been started and the bleaching reaction must be quenched at about the time color reversion starts, preferably by cooling to a temperature below about 8090 C.

The color bodies removed by bleaching of the present invention are peculiar to and are generated by sulfur trioxide in its reaction with olefinic hydrocarbons. By definition, the process is directed to the color improvement of sulfur-trioxide-derived aliphatic sulfonates.

In a preferred embodiment aqueous sodium hypochlorite is added to an aqueous solution of a sulfur-trioxide derived sulfonate while it is being hydrolyzed at about 125 C. Sufficient of the bleach is added to correspond to 3 parts (weight) of bleach for each 100 parts (weight) of the sulfonate. The addition of the hypochlorite is made 5 to 6 minutes prior to the end of the Patented Jan. 4, 1972 hydrolysis reaction period. When the hydrolysis period is completed, the resulting product mixture is then rapidly cooled to a temperature below about C. in order to forestall color reversion. The sulfonate is then further processed as desired, for example. by adjustment of the pH to neutral, titration of unused bleach and spray drying, or the like.

In the bleaching of the sulfur-trioxide-derived sulfonates in the temperature range l00l45 C., there occurs at first a rapid and effective reduction of color of the sulfonate. Thereafter, in general, a rapid reversion in the decolorization action occurs and the color of the sulfonate increases. Effective and useful bleaching of the sulfonate can only be achieved in this color reversion temperature range by quenching the hypochlorite treatment at about the time the reversion commences. These times, i.e., the time, At, from start of bleaching to the time for start of color reversion, t vary depending upon the reaction temperature and are illustrated in FIG. 1 or by the equation wa mwhere At is the total bleaching reaction time in minutes and T is the bleaching temperature in degrees Centigrade.

.To achieve maximum benefit from the bleaching, the time at temperature must be relatively precisely controlled. At the lower end of the temperature range, there is some latitude, i.e., a range of 5l0 minutes, for the control which permits one to achieve effective color reduction. This factor is represented in FIG. 2. For best results, the reaction mixture is heated until the start of the color reversion; and it is then quenched to a temperature in the range of 0 C. to C., preferably 0C. to 80 C.

For rapid bleaching, the temperature must be above about C. On the other hand, the use of temperatures above about C. is not practicable because time to the start of color reversion is so short and the reverse buildup of color bodies is so rapid that control is difficult if not impossible. Above about C., reversion is apparently almost immediate. Below about 80 C. there is no color reversion. For satisfactory bleaching at temperatures below 80 C., however, reaction times are long.

The hypochlorite bleach used in the invention is preferably sodium hypochlorite although alkali metal and alkaline earth metal hypochlorites may also be used. The sodium bleach is an article of commerce and least costly. On the other hand, the alkaline earth bleaches, such as the calcium salt, can be used but they are less desirable by reason of the unfavorable solubility parameter.

The amount of bleach relative to the sulfonate which is desirably used varies, depending: 1) upon the intensity of the color of the sulfonate; (2) the particular bleach to be used; and (3) in lesser degree. the temperature to be employed. In general, a satisfactory amount is in the range from about 0.25 to 5 parts (weight) per 100 parts (weight) of the sulfonate. Larger relative amounts, for example 10 parts of bleach, may be used without substantial adverse effects, but in general such use is uneconomical.

The subject aliphatic sulfonates are generally neutralized and hydrolyzed utilizing aqueous sodium hydroxide or the equivalent. Aqueous solutions or an aqueous medium are therefore preferred for the bleaching. However, polar solvents relatively stable to the bleach may also be used such as aqueous alcohol solutions, and the like.

The concentration of the sulfonate in the bleaching solution may vary widely. As a practical matter, at least a 10 weight percent solution is desirably employed. All of the sulfonate need not be in solution for the bleaching. Thus bleaching is effective Where an aqueous slurry of the sulfonate is used. For mechanical and economical reasons, best results in general follow from the use of aqueous solutions containing from about 20 weight percent up to the saturation value, i.e., usually in the range 50-65 weight percent, of the sulfonate.

The pH of the reaction mixture may be neutral, basic or acidic. As noted above, in the preferred embodiment, bleaching is desirably effected concurrently with hydrolysis. The latter is preferably accomplished using alkali. Thus in the preferred mode, the pH will necessarily range above 7. Large excesses of acid or base are in general desirably avoided. The sulfonates are used in the main as nearly neutral salts. Thus the excess acid or base has to be neutralized, thereby adding salt to the product.

The quenching of the bleaching reaction and avoidance of color reversion may be accomplished by rapid cooling or by chemical means as by reaction of the residual bleaching agent with bisulfite and the like. In the former instance, any suitable cooling means, including he t exchangers, flash evaporation at reduced pressure, dilution with ice or cold water or the like may be utilized for th desired temperature reduction.

In general, the aliphatic sulfonates used for feeds in the instant process are those obtained in sulfonations carried out at temperatures below about 100 C., generally below about 50 C., for the reason that color body production is minimal at the lower temperatures.

In general, the sulfonate feeds used in the instant process will be substantially free of aromatic substituents for the reason that aromatic carbocyclic rings are in general sulfonated under conditions analogous to those conditions where sulfur trioxide reacts with an olefinic hydr carbon. On the other hand, the presence of substantial but minor, i.e., less than 50 percent (mol percent), of an aromatic sulfonate, for example an alkylbenzenesulfonate, does not interfere with color reduction of the subject aliphatic sulfonates.

Aliphatic sulfur-trioxide-derived sulfonates in generally are satisfactorily treated by the instant process, i.e., with a substantial reduction of the color. As a practical matter suitable sulfonate feeds for the instant process will contain from about 8 to 25 carbon atoms, substantial amounts of carbon-carbon unsaturation, substantial amounts of hydroxy substitution and substantial amounts of aliphatic disulfonates, i.e., the feeds will be sulfurtrioxide-derived sulfonates. The suitable sulfonate feeds are conveniently described in terms of the olefinic hydrocarbons used to prepare them, and these include in general all substantially non-aromatic mono-olefinic hydrocarbons. The preferred sulfonate feeds are those *prepared from a-olefins, from the n-a-olefins and from internal n-alkenes. Molecular mixtures as well as individual molecular species are satisfactory feeds. These sulfonate compositions are known to the art and are not per s part of the instant invention except as materials whose color properties are improved by the instant process.

Representative olefin-sulfonate feeds for the present process include those obtained from C -C cracked wax u-olefins, as well as individual molecular range fractions thereof, Cc 30t-Olefi1'1S, C -C internal n-olefins, C -C internal n-olefins; branched chain alkenes such as S-methyl-l-hexadecene; other olefins such as cyclooctene, cyclododecene, vinylcyclohexane, dodecene-2, hexadecene-4, terpines, eicosene-l, nonene-l, octadecene- 5, 4-methylcyclooctene, hendecene-Z, partially isomerized n-m-olefin, i.e., mainly n-alkene-Zs, and the like monoolefinic, non-aromatic hydrocarbons.

The following examples further illustrate th invention though not by way of limitation.

EXAMPLES l-5 Into a pressure vessel fitted for stirring and having a temperature control means was charged and aqueous aliquot of previously hydrolyzed olefin sulfonate obtained by the reaction of sulfur trioxide with a (1 ,-C cracked wax n-a-olefin in about weight percent concentration. When the aliquot was at the desired temperature, suflicient concentrated aqueous sodium hypochlorite solution was then added to correspond to 3 weight percent of the sulfonate. The bleaching reaction was then stopped by rapid quenching of the aliquot to a temperature at which the bleaching action had essentially stopped. The color of the aliquot was then determined by use of a Klett- Summerson photoelectric colorimeter. A series of kinetic runs were made at 80, 100, 115, and C. The data is summarized in FIG. 2.

EXAMPLE 6 As in Example 1, aliquot of a-olefin sulfonate was treated with sodium hypochlorite except that the heating was for a period of two hours at a temperature where color reversion does not occur, i.e., one hour each at 50 C. and 80 C. The aliquot was then rapidly heated to a temperature above about 115 C. The expected color reversion of the sample in view of Examples 1-5 oc curred.

It will be readily appreciated from the above disclosure and examples that variations can be made therein and equivalents may be substituted without going beyond the purview of the invention or exceeding the scope of the claims.

I claim:

1. The method of avoiding color reversion in the alkali or alkaline earth metal hypochlorite bleaching of a sulfonate in an aqueous solution or medium at a temperature in the range from about 100 C. to C., wherein the sulfonate is obtained by the reaction of sulfur trioxide with a substantially nonaromatic monoolefinic hydrocarbon having a carbon atom content in the range from about 8 to 25 and wherein in parts by weight for each 100 parts of the sulfonate an amount of said bleach in the range from about 0.25 to 10 parts is present in the aqueous solution or medium, which comprises heating the aqueous solution or medium until about the start of the color reversion and thereafter quenching the bleaching reaction by cooling the aqueous solution or medium to a temperature in the range from about 0 C. to 8090 C. or by reaction of the residual bleaching agent with hisulfite.

2. The method as in claim 1 wherein the quenching is effected by cooling the aqueous solution or medium to a temperature in the range from about 0 C. to 8090 C.

3. The method as in claim 1 wherein the bleaching reaction is quenched by bisulfite.

4. The method as in claim 1 wherein the hydrocarbon is an n-alkene having a carbon atom content in the range from about 8 to 25.

5. The method as in claim 1 wherein said bleach is sodium hypochlorite.

6. The method of avoiding color reversion in the alkali or alkaline earth metal hypochlorite bleaching of a sulfonate in an aqueous solution or medium at a temperature in the range from about 100 C. to 145 C., wherein the sulfonate is obtained by the reaction of sulfur trioxide with an n-alkene having a carbon atom content in the range from about 8 to 25 and wherein in parts by weight for each 100 parts of the sulfonate an amount of said bleach in the range from about 0.25 to 10 parts is present in the aqueous solution or medium, which comprises heating the aqueous solution or medium for a period defined by the expression At=(147T) +2.28

wherein Z is the total bleaching reaction time in minutes and T is the bleaching reaction temperature in degrees centigrade and thereafter quenching the bleaching reaction by cooling the aqueous solution or medium to a temperature in the range from about 0 C. to 80-90 C. or by reaction of the residual bleaching agent with bisulfite.

7. The method of claim 6 wherein the quenching is effected by cooling the aqueous solution or medium to a temperature in the range from about 0 C. to 8090 C.

5 6 8. The method of claim 6 wherein the quenching is 2,880,235 3/1959 Weaver et a1. 202-161 X effected by bisulfite. 2,975,141 3/1961 Blinoff et a1. 252-95 X 9. The method as in claim 6 wherein said bleach is sodium hypochlorite. MAYER WEINBLATT, Primary Examiner References Cited 5 C1 

